Implantable medical device with constrained expansion

ABSTRACT

Medical devices for implantation in a body vessel are provided. A medical device according to the invention comprises a support structure and one or more graft members comprising a valve portion and a constraining portion. The support structure has a first, unexpanded configuration and a second, expanded configuration. The constraining portion is adapted to substantially prevent the support structure from achieving the second, expanded configuration. The valve portion is adapted to permit fluid flow through a body vessel in a first direction and substantially prevent fluid flow through the vessel in a second, opposite direction.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional ApplicationSer. No. 60/471,647, filed on May 19, 2003, the entire disclosure ofwhich is hereby incorporated into this disclosure in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to medical devices. Moreparticularly, the invention relates to medical devices for implantationin a body vessel.

BACKGROUND OF THE INVENTION

[0003] Many vessels in animals transport fluids from one bodily locationto another. Frequently, fluid flows in a unidirectional manner along thelength of the vessel. Varying fluid pressures over time, however, canintroduce a reverse flow direction in the vessel. In some vessels, suchas mammalian veins, natural valves are positioned along the length ofthe vessel and act as one-way check valves that open to permit the flowof fluid in the desired direction, and quickly close upon a change inpressure, such as a transition from systole to diastole, to preventfluid flow in a reverse direction, i.e., retrograde flow.

[0004] While natural valves may function for an extended time, some maylose effectiveness, which can lead to physical manifestations andpathology. For example, venous valves are susceptible to becominginsufficient due to one or more of a variety of factors. Over time, thevessel wall may stretch, affecting the ability of the valve leaflets toclose. Furthermore, the leaflets may become damaged, such as byformation of thrombus and scar tissue, which may also affect the abilityof the valve leaflets to close. Once valves are damaged, venous valveinsufficiency may be present, and can lead to discomfort and possiblyulcers in the legs and ankles.

[0005] Current treatments for venous valve insufficiency include the useof compression stockings that are placed around the leg of a patient inan effort to force the vessel walls radially inward to restore valvefunction. Surgical techniques are also employed in which valves can bebypassed or replaced with autologous sections of veins with competentvalves.

[0006] Minimally invasive techniques and instruments for placement ofintraluminal medical devices have developed over recent years. A widevariety of treatment devices that utilize minimally invasive technologyhas been developed and includes stents, stent grafts, occlusion devices,infusion catheters and the like. Minimally invasive intravasculardevices have especially become popular with the introduction of coronarystents to the U.S. market in the early 1990's. Coronary and peripheralstents have been proven to provide a superior means of maintainingvessel patency, and have become widely accepted in the medicalcommunity. Furthermore, the use of stents has been extended to treataneurisms and to provide occlusion devices, among other uses.

[0007] Recently, prosthetic valves have been developed that use asupport structure such as a stent. Frequently, a graft member isattached to the support structure and provides a valve function to thedevice. For example, the graft member can be in the form of a leafletthat is attached to a stent and movable between first and secondpositions. In a first position, the valve is open and allows fluid flowto proceed through a vessel in a first direction, and in a secondposition the valve is closed to prevent fluid flow in a second, oppositedirection. An example of this type of prosthetic valve is described incommonly owned U.S. Pat. No. 6,508,833, to Pavcnik for a MULTIPLE-SIDEDINTRALUMINAL MEDICAL DEVICE, which is hereby incorporated by referencein its entirety. In other examples of prosthetic valves, a tube thatterminates in leaflets is attached to one or more support structures toform a valve. The leaflets open to permit fluid flow in a firstdirection in response to fluid pressure on one side of the leaflets, andclose to prevent fluid flow in a second, opposite direction in responseto fluid pressure on opposite sides of the leaflets. An example of thisconfiguration is provided in U.S. Pat. No. 6,494,909 to Greenhalgh forAN ENDOVASCULAR VALVE, which is hereby incorporated by reference in itsentirety.

[0008] Support structures in some medical devices, such as stent grafts,can exert an outwardly-directed radial force upon an interior wall of abody vessel in which such a medical device is implanted. The exertion ofsuch a force has potential to induce an inflammatory response or othereffect within the body vessel and/or the surrounding tissue.Accordingly, medical devices with constrained expansion are desirable.

SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0009] The invention provides medical devices for implantation in a bodyvessel.

[0010] In one exemplary embodiment, a medical device according to theinvention comprises a support structure having a first, unexpandedconfiguration and a second, expanded configuration, and a graft memberconnected to the support structure. The a graft member comprises a valveportion and a constraining portion. The valve portion is adapted topermit fluid flow through a body vessel in a first direction andsubstantially prevent fluid flow through the vessel in a second,opposite direction. The constraining portion is adapted to substantiallyprevent the support structure from achieving the second, expandedconfiguration.

[0011] In one exemplary embodiment, a medical device according to theinvention comprises a support structure and first and second graftmembers connected to the support structure. Each of the graft memberscomprises a valve portion and a constraining portion. The valve portionsare disposed substantially opposite one another and are adapted topermit fluid flow through a body vessel in a first direction andsubstantially prevent fluid flow through the vessel in a second,opposite direction. The constraining portions cooperate to substantiallyprevent the support structure from achieving the second, expandedconfiguration.

[0012] In one exemplary embodiment, a medical device according to theinvention comprises a support structure having a first, unexpandedconfiguration and a second, expanded configuration, means for preventingthe support structure from achieving the second, expanded configuration,and means for regulating fluid flow through a body vessel.

[0013] In one exemplary embodiment, a medical device according to theinvention comprises a support structure having a first, unexpandedconfiguration and a second, expanded configuration, a first valveleaflet connected to the support structure and comprising a first valveportion and a first constraining portion, and a second valve leafletconnected to the support structure and comprising a second valve portionand a second constraining portion. The first and second valve portionscooperatively regulate fluid flow through a body vessel, and the firstand second constraining portions cooperatively prevent the supportstructure from achieving the second, expanded configuration.

[0014] In one exemplary embodiment, a medical device according to theinvention comprises a support structure having a first, unexpandedconfiguration and a second, expanded configuration. The device furthercomprises a first graft member attached to the support structure, havinga first edge, and adapted to permit fluid flow through said vessel in afirst direction and substantially prevent fluid flow through said vesselin a second, opposite direction. The device further comprises a secondgraft member attached to the support structure, having a second edge,and adapted to substantially prevent the support structure fromachieving the second, expanded configuration. The first and second edgescooperatively define an opening adapted to permit a controlled amount offluid flow through a body vessel in the second, opposite direction.

[0015] The invention also provides methods of making a medical device.In one exemplary embodiment, a method of making according to theinvention comprises providing a support structure having a first,unexpanded configuration and a second, expanded configuration, providinga graft member, attaching the graft member to the support structure,forming a valve portion in the graft member, and constraining thesupport structure to substantially prevent the support structure fromachieving the second, expanded configuration.

[0016] The invention also provides methods of treating a patient. In oneexemplary embodiment, a method of treating a patient according to theinvention comprises providing a medical device comprising a supportstructure having a first, unexpanded configuration and constrained fromachieving a second, expanded configuration, and a graft member attachedto the support structure, the graft member comprising a valve portionadapted to permit fluid flow through said vessel in a first directionand substantially prevent fluid flow through said vessel in a second,opposite direction. The method of treating further comprises deliveringthe medical device to a point of treatment in a body vessel, anddeploying the medical device at the point of treatment.

[0017] The invention includes other embodiments within the scope of theclaims, and variations of all embodiments, and is limited only by theclaims made by the applicant. Additional understanding of the inventioncan be obtained by referencing the detailed description of exemplaryembodiments of the invention, below, and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view of a medical device according to afirst exemplary embodiment of the invention.

[0019]FIG. 2 is a side view of the medical device illustrated in FIG. 1.

[0020]FIG. 3 is a perspective view of the medical device illustrated inFIG. 1 showing the device in an open configuration.

[0021]FIG. 4 is a side view of the medical device illustrated in FIG. 3.

[0022]FIG. 5 is a perspective view of the medical device illustrated inFIG. 1 showing the device in a closed configuration.

[0023]FIG. 6 is a side view of the medical device illustrated in FIG. 5.

[0024]FIG. 7 is a perspective view of a medical device according to asecond exemplary embodiment of the invention.

[0025]FIG. 8 is a sectional view of the medical device illustrated inFIG. 7 taken along line 8-8.

[0026]FIG. 9 is a perspective view of a medical device according to athird exemplary embodiment of the invention.

[0027]FIG. 10 is a perspective view of a medical device according to afourth exemplary embodiment of the invention.

[0028]FIG. 11 is a perspective view of a medical device according to afifth exemplary embodiment of the invention.

[0029]FIG. 12 is a perspective view of a medical device according to asixth exemplary embodiment of the invention.

[0030]FIG. 13 is a perspective view of the support structure of themedical device illustrated in FIG. 12.

[0031]FIG. 14 is a side view of the graft member of the medical deviceillustrated in FIG. 11.

[0032]FIG. 15 is a perspective view of a medical device according to aseventh exemplary embodiment of the invention.

[0033]FIG. 16 is a perspective view of a medical device according to aneighth exemplary embodiment of the invention.

[0034]FIG. 17 is a flow chart of a method of making a medical deviceaccording to the invention.

[0035]FIG. 18 is a flow chart of a method of treatment according to theinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0036] The following detailed description and appended drawings describeand illustrate various exemplary embodiments of the invention. Thedescription and drawings serve to enable one skilled in the art to makeand use the invention, and are not intended to limit the scope of theinvention or its protection in any manner.

[0037] The invention provides medical devices for implantation in a bodyvessel, methods of making the medical devices, and methods of treatmentthat utilize the medical devices.

[0038]FIGS. 1 through 6 illustrate a medical device 10 according to afirst exemplary embodiment of the invention. The device 10 is animplantable medical device that comprises a support structure 12 andfirst 14 and second 16 graft members attached to the support structure12.

[0039] As used herein, the term “implantable” refers to an ability of amedical device to be positioned at a location within a body, such aswithin a body vessel. Furthermore, the terms “implantation” and“implanted” refer to the positioning of a medical device at a locationwithin a body, such as within a body vessel.

[0040] A wide variety of support structures are known in the art, andany suitable support structure can be utilized. The support structurechosen need only provide a structure for attachment of the graft members14, 16. A support structure that provides a stenting function, i.e.,exerts a radially outward force on the interior of the vessel in whichthe device 10 is implanted, can be utilized if desired. By including asupport structure that provides a stenting function, the medical device10 can provide both stenting and valving functionality at a point oftreatment.

[0041] The stent art provides numerous examples of support structuresacceptable for use in the medical device 10, and any suitable stentsupport structure can be used. The specific support structure chosenwill depend on several factors, including the vessel in which themedical device is being implanted, the axial length of the treatmentsite, the number of valves desired in the device, the inner diameter ofthe vessel, the delivery method for placing the support structure, andothers. Those skilled in the art can determine an appropriate supportstructure based on these and other factors.

[0042] The support structure 12 is an expandable support structurehaving a first, unexpanded configuration and a second, expandedconfiguration. The support structure 12 can be either balloon- orself-expandable. Also, the support structure can be formed from avariety of materials, and need only be biocompatible, or able to be madebiocompatible, and provide for the attachment of the graft members 14,16 and stenting function, if desired. Examples of suitable materialsinclude, without limitation, stainless steel, nickel titanium (NiTi)alloys, e.g., Nitinol, other shape memory and/or superelastic materials,polymers, and composite materials. A resorbable material can also beused for the support structure 12. As used herein, the term “resorbable”refers to the ability of a material to be absorbed into a tissue and/orbody fluid upon contact with the tissue and/or body fluid. A number ofresorbable materials are known in the art, and any suitable resorbablematerial can be used. Examples of suitable types of resorbable materialsinclude resorbable homopolymers, copolymers, or blends of resorbablepolymers. Specific examples of suitable resorbable materials includepoly-alpha hydroxy acids such as polylactic acid, polylactide,polyglycolic acid (PGA), or polyglycolide; trimethlyene carbonate;polycaprolactone; poly-beta hydroxy acids such as polyhydroxybutyrate orpolyhydroxyvalerate; or other polymers such as polyphosphazines,polyorganophosphazines, polyanhydrides, polyesteramides,polyorthoesters, polyethylene oxide, polyester-ethers (e.g.,polydioxanone) or polyamino acids (e.g., poly-L-glutamic acid orpoly-L-lysine). There are also a number of naturally derived resorbablepolymers that may be suitable, including modified polysaccharides, suchas cellulose, chitin, and dextran, and modified proteins, such as fibrinand casein.

[0043] Suitable support structures can also have a variety ofconfigurations, including braided strands, helically wound strands, ringmembers, consecutively attached ring members, tube members, and framescut from solid tubes. Also, suitable support structures can have avariety of sizes. The exact configuration and size chosen will depend onseveral factors, including the desired delivery technique, the nature ofthe vessel in which the device will be implanted, and the size of thevessel. The support structure can be sized so that the second, expandedconfiguration is larger in diameter that the inner diameter of thevessel in which the device will be implanted. This sizing can facilitatemaintenance of the device in the vessel following implantation.

[0044] Examples of suitable support structures for use in the medicaldevices of the invention include those described in U.S. Pat. No.6,508,833 to Pavcnik et al. for a MULTIPLE-SIDED INTRALUMIINA MEDICALDEVICE; U.S. Pat. No. 6,464,720 to Boatman et al. for a RADIALLYEXPANDABLE STENT; U.S. Pat. No. 6,231,598 to Berry et al. for a RADIALLYEXPANDABLE STENT; U.S. Pat. No. 6,299,635 to Frantzen for a RADIALLYEXPANDABLE NON-AXIALLY CONTRACTING SURGICAL STENT; U.S. Pat. No.4,580,568 to Gianturco for a PERCUTANEOUS ENDOVASCULAR STENT AND METHODFOR INSERTION THEREOF; and published application for United StatesPatent 2,001,0039450 to Pavcnik et al. for an IMPLANTABLE MEDICALDEVICE, all of which are hereby incorporated by reference in theirentirety.

[0045] The support structure 12 can include structural features, such asbarbs 22, that maintain the support structure 12 in position followingimplantation in a body vessel. The art provides a wide variety ofstructural features that are acceptable for use in the medical device10, and any suitable structural feature can be used. Furthermore, barbs22 can also comprise separate members attached to the support structure12 by suitable attachment means and techniques, such as welding andbonding.

[0046] A wide variety of materials acceptable for use as the graftmembers 14, 16 are known in the art, and any suitable material can beutilized. The material chosen need only be able to perform as describedherein, and be biocompatible, or able to be made biocompatible. Examplesof suitable materials include flexible materials, natural materials,synthetic materials, and combinations thereof. Examples of suitablenatural materials include collagen, extracellular matrix (ECM)materials, such as submucosa, and other bioremodellable materials, suchas bovine pericardium. Small intestine submucosa (SIS) is particularlywell-suited for use as the graft members 14, 16. Other examples of ECMmaterials that can be used for the graft member include stomachsubmucosa, liver basement membrane, urinary bladder submucosa, tissuemucosa, and dura mater. ECMs are particularly well suited materials foruse in the graft member, at least because of their abilities to remodeland become incorporated into adjacent tissues. These materials canprovide a scaffold onto which cellular in-growth can occur, eventuallyallowing the material to remodel into a structure of host cells.

[0047] Examples of suitable synthetic materials include polymericmaterials, such as polypropylene, polyurethane, and expandedpolytetrafluoroethylene (ePTFE).

[0048] As best illustrated in FIGS. 1 through 4, free edges 19, 21 ofthe graft members 14, 16 cooperatively define an opening 18. The graftmembers 14, 16 can be attached to the support structure 12 with anysuitable attachment mechanism, such as sutures 20, adhesives, bonding,and the like. The attachment mechanism chosen will depend on the natureof the support structure 12 and graft members 14, 16. Sutures 20 providean acceptable attachment mechanism when SIS or other ECM materials areused as the graft members 14, 16 with a metal or plastic supportstructure.

[0049] The device 10 can include any suitable number of graft members.The graft members need only be able to provide the functionalitydescribed herein. The specific number chosen will depend on severalfactors, including the type and configuration of the support structure12. As illustrated in FIGS. 1 through 6, two graft members 14, 16 aresuitable for use in devices 10 comprising a support structure configuredin accordance with this embodiment, but a single graft member, or threeor more graft members, can also be used.

[0050] The graft members 14, 16 comprise a constraining portion 23 and avalve portion 29. The constraining portion is adapted to substantiallyprevent the support structure 12 from achieving the second, expandedconfiguration. This prevents the valve portion 29 from becomingcompletely taught. The constraining portion 23 is sized such that, asthe support structure expands from the first configuration to the secondconfiguration, the constraining portion 23 becomes taught, substantiallypreventing further expansion of the support structure 12. As describedmore fully below, the constraining portion 23 can be sized such that theconstrained configuration of the device 10 is slightly larger indiameter than the inner diameter of the vessel in which the device willbe implanted, but less than a vessel inner diameter at which an adverseeffect may occur, such as vessel rupture. This sizing can facilitatemaintenance of the device 10 in the vessel following implantation.

[0051] As best illustrated in FIGS. 1, 3, and 5, the medical device 10of the first embodiment, includes a constraining portion 23 thatcomprises a gathered portion 24 of the material of the graft members 14,16. The gathered portion 24 comprises two non-contiguous regions of anindividual graft member 14, 16 that are drawn together to exclude anintervening portion 26. The non-contiguous regions are held together byany suitable connecting mechanism, such as sutures 28.

[0052] The valve portion 29 is adapted to permit fluid flow through thebody vessel in a first direction, represented by arrow 45 in FIGS. 3 and4, and substantially prevent fluid flow through the body vessel in asecond, opposite direction, represented by arrow 47 in FIGS. 5 and 6.The valve portion 29 can move between first and second positions to openand close the opening 18 and alternately permit and substantiallyprevent fluid flow through the opening.

[0053] As best illustrated in FIG. 1, the valve portion 29 can includepleats 30. As used herein, the term “pleat” refers to a fold, crease,bend or other transition in the material of a graft member. The termdoes not specifically require a permanent or semi-permanent crease inthe material. As best illustrated in FIGS. 3 and 4, the valve portion 29opens to enlarge opening 18 to permit fluid flow through the opening 18,and through the body vessel in which the device 10 is implanted, in afirst direction 45. As best illustrated in FIGS. 5 and 6, the valveportion 29 closes opening 18 (not referenced in FIGS. 5 and 6, butcontrast FIGS. 3 and 4) to substantially prevent fluid flow through theopening 18, and through the body vessel in which the device 10 isimplanted, in a second, opposite direction 47. In this embodiment, thepleats 30 provide extra material in the valve portion 29 to ensureclosure of the opening 18 when the valve portion 29 moves to a closedposition.

[0054] The valve portion 29 can move between the open and closedconfigurations in response to a change in direction of fluid flow, suchas a change from flow in the first direction 45 to a change of flow inthe second, opposite direction 47. Also, the valve portion can movebetween open and closed configurations in response to a change in fluidpressure on one or more sides of the graft members 14, 16.

[0055] As illustrated in FIG. 6, the valve portions 29 can includesufficient material to form a coaptation region 32 between the graftmembers 14, 16. The coaptation region 32 is a length along which thegraft members 14, 16 contact each other when the valve portions 29 ofthe graft members 14, 16 are in a closed configuration.

[0056]FIGS. 7 and 8 illustrate a medical device 110 according to asecond exemplary embodiment of the invention. The device 110 illustratedin FIGS. 7 and 8 is similar to the device 10 illustrated in FIGS. 1through 6, except as detailed below. Thus, the device 110 of thisembodiment includes a support structure 112, graft members 114, 116,sutures 120, barbs 122, constraining portion 123, gathered portion 124,intervening portion 126, sutures 128, and valve portion 129. FIG. 7illustrates the device 110 having the valve portion 129 in a closedconfiguration to substantially prevent fluid flow in the second oppositedirection 147. The valve portion 129 operates in a manner similar to thevalve portion 29 of the device 10 illustrated in FIGS. 1 through 6.

[0057] The medical device 110 includes passageway 134 in graft member114 that allows a controlled amount 135 of fluid flow in the second,opposite direction to flow through the vessel in which the device 110 isimplanted. The controlled amount 135 of flow is a portion of fluid flow147. The passageway 134 defines a path extending from one portion, suchas valve portion 129 or an upper part of constraining portion 123, ofthe device 110 to a second portion, such as a lower portion of theconstraining portion 123, of the device 110. In the embodimentillustrated in FIG. 7, the gathered portion 124 defines the passageway134.

[0058] The passageway 134 can have any suitable configuration,cross-sectional area, and length. The overall configuration,cross-sectional area, and length selected for the passageway 134 willdepend on several factors, including the size and configuration ofdevice 110, the size and configuration of the vessel in which the device110 will be implanted, the extent of contact between the device 110 andthe walls of the vessel, and the amount of retrograde flow through thevessel that is desired.

[0059]FIG. 9 illustrates a medical device 210 according to a thirdexemplary embodiment of the invention. The device 210 illustrated inFIG. 9 is similar to the device 110 illustrated in FIGS. 7 and 8, exceptas detailed below. Thus, the device 210 of this embodiment includes asupport structure 212, graft members 214, 216, sutures 220, barbs 222,constraining portion 223, gathered portion 224, intervening portion 226,sutures 228, and valve portion 229. Also, the device 210 includespassageway 234. FIG. 9 illustrates the device 210 having the valveportion 229 in a closed configuration to substantially prevent fluidflow in the second opposite direction 247. The valve portion 229operates in a manner similar to the valve portion 29 of the device 10illustrated in FIGS. 1 through 6.

[0060] The medical device 210 includes a conduit 236 disposed inpassageway 234. Conduit 236 can provide reinforcement to passageway 234,and may provide an interior surface of a material different than that ofpassageway 234. Conduit 236 can be formed of any suitable material, suchas naturally occurring or synthetic materials, including polymerictubing. The size and configuration of conduit 236 will largely depend onthe size and configuration of passageway 234. Conduit 236 should besized such that it can be retained in passageway 234 under physiologicalloads, either by friction fit, a suitable attachment mechanism, such assutures, or any other suitable mechanism. Also, conduit 236 can belonger, shorter, or have the same length as passageway 234.

[0061] As illustrated in FIG. 9, conduit 236 includes an opening 238that permits the exit of the controlled amount 235 of fluid flow fromthe passageway 234. Opening 238 can be defined by a beveled edge 240 onconduit 236. Beveled edge 240 can define a taper toward or away from thewall surface of the vessel in which the medical device 210 will beimplanted.

[0062]FIG. 10 illustrates a medical device 310 according to a fourthexemplary embodiment of the invention. The device 310 illustrated inFIG. 10 is similar to the device 10 illustrated in FIGS. 1 through 6,except as detailed below. Thus, the device 310 of this embodimentincludes a support structure 312, graft members 314,316, sutures 320,barbs 322, constraining portion 323, gathered portion 324, interveningportion 326, sutures 328, and valve portion 329. Free edges 319, 321 ofthe graft members 314, 316 cooperatively define an opening 318, and thevalve portion 329 includes pleats 330. The valve portion 329 operates ina manner similar to the valve portion 29 of the device 10 illustrated inFIGS. 1 through 6.

[0063] Medical device 310 includes at least one opening 350 that permitsa controlled amount of fluid flow in the second, opposite direction toflow through the vessel in which the device 310 is implanted. In thisembodiment, the opening 350 is defined by an edge 354 of the graftmember 314 and a portion 352 of the support structure 312. Opening 354could also comprise a slit or other aperture in the graft member 314.

[0064] As illustrated in FIG. 10, the device can include first 350 andsecond 351 openings that permit a controlled amount of fluid flow in thesecond, opposite direction. If present, second opening 351 can bedefined in a manner similar to that of opening 350, i.e., by an edge 355of the graft member 316 and a portion 353 of the support structure 312,or in any other suitable manner, such as those described and illustratedherein.

[0065]FIG. 11 illustrates a medical device 410 according to a fifthexemplary embodiment of the invention. The device 410 illustrated inFIG. 11 is similar to the device 10 illustrated in FIGS. 1 through 6,except as detailed below. Thus, the device 410 of this embodimentincludes a support structure 412, graft members, sutures 420, barbs 422,constraining portion 423, and valve portion 429. Free edges 419, 421 ofthe graft members 414 a, 416 a cooperatively define opening 418, and thevalve portion 429 includes pleats 430. The valve portion 429 operates ina manner similar to the valve portion 29 of the device 10 illustrated inFIGS. 1 through 6.

[0066] Medical device 410 includes an opening 460 defined by free edges415, 417 of first 414 a and second 414 b graft members, respectively.Opening 460 permits a controlled amount of fluid flow in the second,opposite direction to flow through the vessel in which the device 410 isimplanted. The first graft member 414 a can form the valve portion 429,and the second graft member 414 b can form the constraining portion 423.Opening 460 can also comprise a slit or other aperture in a single graftmember.

[0067] As illustrated in FIG. 11, device 410 can include first 460 andsecond 461 openings that permit a controlled amount of fluid flow in thesecond, opposite direction. If present, the second opening 461 can bedefined in a manner similar to that of opening 460, i.e., by edges 425and 427 of third 416 a and fourth 416 b graft members, or in any othersuitable manner, such as those described and illustrated herein.

[0068] In this embodiment, the graft members 414 a, 414 b, 416 a, 416 bcan be formed of the same or different materials. The use of differentmaterials may be advantageous at least because it provides a degree ofcontrol to the constrained expansion. For example, two materials havingdifferent compliance properties could be used. In one exemplaryembodiment, the first graft member 414 a is formed of a material that ismore compliant than the material from which the second graft member 414b is formed. This configuration allows the second graft member 414 b toconstrain the expansion of the support structure 412, thereby providingthe constraining portion 423, and allows the first graft member 414 a toprovide the valve portion 429.

[0069] If two different materials are desired, any suitable pairing ofmaterials can be used. The materials chosen need only have the desireddifference in compliance properties or in any other desired property.

[0070] An example of a suitable pairing of materials is a naturalmaterial and a synthetic material. In one exemplary embodiment, apolymer, such as polypropylene, is used to form one graft member and anextracellular matrix material, such as submucosa, is used to formanother graft member. Furthermore, the graft members 414 a, 414 b can beformed of the same material, but can be treated, or processed, or madein different manners that produce the desired different properties. Forexample, one graft member can be formed from a extracellular matrixmaterial and another graft member can be formed of an extracellularmatrix material that has been fixed, such as by chemical processing.

[0071] In embodiments in which two materials are used, the materials canbe disposed on the support structure in a manner that forms an opening,such as the opening 460 illustrated in FIG. 11, or the materials can beattached to each other in any suitable manner to partially or completelyeliminate any opening between the graft members. For example, the twograft members can be joined by an attachment element, such as a suture,an adhesive, or a clip. Also, the graft members can be joined together,such as by tissue welding, melt forming, or any other suitable process.

[0072] In the embodiments that include openings that permit a controlledamount of fluid flow in the second, opposite direction to flow throughthe vessel in which the device is implanted, the dimensions,configuration, and number of the openings can be optimized based uponthe vessel in which the device is implanted. The size and configurationselected will depend on several factors, including the vessel size,typical flow volumes and rates, and others. The opening should be sizedto allow a desired amount of retrograde flow to occur, while remainingsufficiently small to still allow the medical device to act as a valve.Thus, the opening can be sized so as to not allow a majority ofretrograde flow to pass through the opening. The total open area of theopening should be less than the cross-sectional area of the vessellumen.

[0073] The opening can be sized to mimic the degree of retrogradeflow—the leakiness—that is present in a natural valve located at thepoint of treatment. In these embodiments, the dimensions of the openingcan be determined and optimized based upon the vessel in which thedevice is to be placed. The total open area of the opening can be lessthan about 50% of the cross-sectional area of the vessel, or less thanabout 25% of the total cross-sectional area of the vessel. In oneparticular example, a device is configured for placement in a vesselhaving a total cross-sectional area of about 50 mm². In this example,the opening has a total open area of about 20 mm².

[0074] In devices including multiple openings that permit a controlledamount of fluid flow in the second, opposite direction to flow throughthe vessel in which the device is implanted, the total open area of allopenings can be optimized as described above, but it is not necessarythat the individual openings have equivalent total open areas.

[0075]FIG. 12 illustrates a medical device 510 according to a sixthexemplary embodiment of the invention. The device 510 illustrated inFIG. 12 is similar to the device 10 illustrated in FIGS. 1 through 6,except as detailed below. Thus, the device 510 of this embodimentincludes a support structure 512, sutures 520, barbs 522, constrainingportion 523, and valve portion 529. Free edges 519, 521 of the graftmembers 570, 572 cooperatively define opening 518, and the valve portion529 includes pleats 530. The valve portion 529 operates in a mannersimilar to the valve portion 29 of the device 10 illustrated in FIGS. 1through 6. FIG. 13 illustrates the support structure 512 of the device510 illustrated in FIG. 12, without the attached graft members 570, 572.FIG. 14 illustrates one graft member 570 prior to attachment to thesupport structure 512.

[0076] In this embodiment, graft members 570, 572 are configured to haveat least two distinct portions 13 and 14 that individually correspond tothe valve 529 and constraining portions 523. The portions 13, 14 differfrom each other in at least one dimension. For example, FIG. 14illustrates portion 13 as having a width w, that is greater than a widthw₂ of portion 14. When graft member 570 is attached to support structure512, support structure 512 is constrained by the smaller width w₂ ofportion 14, while support structure 512 is not constrained, or isconstrained to a lesser degree, by the larger width w₁ of portion 13.Thus, in device 510, portion 14 is drawn taught, providing constrainingportion 523, while portion 13 is not taught, providing pleats 530 andvalve portion 529. This configuration of graft members 570, 572 mayeliminate the need for a gathered portion, such as gathered portion 24of the device 10 illustrated in FIGS. 1 through 6.

[0077] As illustrated in FIG. 14, graft member 570 may includetransition portion 15 that defines a taper between the larger width w₁of portion l₃ and the smaller width w₂ of portion l₄.

[0078]FIG. 15 illustrates a medical device 610 according to a seventhexemplary embodiment of the invention. The device 610 of this embodimentincludes a support structure 612 and first 614 and second 616 graftmembers. Each graft member 614, 616 is attached to the support structure612 by attachment elements, such as sutures 618. Free edges 620, 622 ofgraft members 614, 616, respectively, cooperatively define an opening624. Together, the graft members 614, 616 permit fluid flow through abody vessel in which the device 610 is implanted in a first directionand substantially prevent fluid flow through the body vessel in asecond, opposite direction. The graft members 614, 616 accomplish thisby opening and closing the opening 624 in response to changes inpressure, fluid flow direction, or other parameters.

[0079] In this embodiment, the support structure is prevented fromachieving its second, expanded configuration by a constraining member626 that is attached to the support structure 612 and is distinct fromthe graft members 614, 616. In the embodiment illustrated in FIG. 15,the constraining member 626 comprises a suture tied to opposite portionsof the support structure and disposed across a graft member 614. Theconstraining member 626 can be disposed at any suitable positions on thesupport structure 612, such as at or below a midpoint relative to theopening 624 and the opposing end of the support structure 612.

[0080]FIG. 16 illustrates a medical device 710 according to an eighthexemplary embodiment of the invention. The device 710 of this embodimentis similar to the device 610 illustrated in FIG. 15, except as describedbelow. Thus, the device 710 includes a support structure 712, and first714 and second 716 graft members attached to the support structure 712by attachment elements, such as sutures (not illustrated in FIG. 16).Free edges 720, 722 of graft members 714, 716, respectively,cooperatively define an opening 724. Together, the graft members 714,716 permit fluid flow through a body vessel in which the device 710 isimplanted in a first direction and substantially prevent fluid flowthrough the body vessel in a second, opposite direction. The graftmembers 714, 716 accomplish this by opening and closing the opening 724in response to changes in pressure, fluid flow direction, or otherparameters.

[0081] In this embodiment, the support structure 712 is prevented fromachieving its second, expanded configuration by a constraining member726 disposed about the support structure 712 and is distinct from thegraft members 714, 716.

[0082] In the illustrated embodiment, the constraining member 726comprises a sleeve disposed circumferentially about the supportstructure 712. The constraining member 726 can be attached to thesupport structure 712 or other portion of the medical device, such asgraft members 712, 714, by any suitable attachment element, such asadhesives, sutures, and thermal bonding. Alternatively, the constrainingmember 726 can be secured to the support structure 712 through aninterference fit that arises due to the constraining nature of theconstraining member 726.

[0083] In all embodiments, the support structure of the medical devicecan be constrained to any suitable degree relative to its second,expanded configuration. It is expected to be advantageous to constrainthe support structure to a degree that allows the medical device toachieve a diameter from implantation that is larger than the restingdiameter of the body vessel in which the device is implanted but that issmaller than a diameter at which an adverse effect can occur, such asrupture of the body vessel. For example, a prosthetic venous valveaccording to one exemplary embodiment of the invention is designed forimplantation in a vein. It is expected that the prosthetic valve will beadvantageous if the support structure is constrained from expandingbeyond about 1.5 times the resting diameter of the body vessel at adesired point of implantation. It is expected to be particularlyadvantageous for the support structure to be constrained from expandingbeyond about 1.2 times the resting diameter of the body vessel at adesired point of implantation.

[0084] The invention also provides methods of making medical devices forimplantation in a body vessel. FIG. 17 illustrates a flow chart of amethod 800 according to one embodiment of the invention. The methodcomprises a step 802 of providing a support structure, a step 804 ofproviding a graft member, a step 806 of attaching the graft member tothe support structure, a step 808 of forming a valve portion, and a step810 of constraining the support structure. In the constraining step 810of one exemplary method according to the invention, a graft member ismanipulated so that a portion of the graft member constrains theexpansion of the support structure but the valve portion does notconstrain the support structure, or does so to a lesser degree thananother portion of the graft member. The step 808 of forming a valveportion and the step 810 of constraining the support structure can beaccomplished in one step that achieves both functions. For example, thesupport structure and graft member can be disposed, together, on amandrel with structural features that are complementary to the valve andconstraining portions of the medical device. The mandrel can define arecess that allows slack in an area that will become the valve portion,and can define a structural feature that draws the graft member taughtin an area that will become the constraining portion. The material canbe placed on such a mandrel, and the support structure can then bedisposed on the material. While the assembly is still on the mandrel,the graft member can be attached to the support structure. With somematerials, such as extracellular matrix materials, it may beadvantageous to keep the materials wet during some or all manufacturingsteps. This is expected to provide a desired degree of control over theformation of the valve and/or constraining portions.

[0085] The invention also provides methods of treating a patient. FIG.18 illustrates a flow chart of a method according to one embodiment ofthe invention. The method 900 comprises a step 902 of providing amedical device according to the invention, a step 904 of delivering themedical device to a point of treatment in a body vessel, and a step 906of deploying the medical device at the point of treatment. Thedelivering step 904 can comprise delivery by surgical or by percutaneousdelivery techniques known to those skilled in the art.

[0086] The foregoing description of exemplary embodiments of theinvention includes the best mode for practicing the invention. It isintended to aid in the understanding of the invention, and not to limitthe invention or its protection in any manner.

We claim:
 1. A medical device for implantation in a body vessel,comprising: a support structure having a first, unexpanded configurationand a second, expanded configuration; and a graft member connected tothe support structure and comprising a valve portion and a constrainingportion, the valve portion adapted to permit fluid flow through saidvessel in a first direction and substantially prevent fluid flow throughsaid vessel in a second, opposite direction, and the constrainingportion adapted to substantially prevent the support structure fromachieving the second, expanded configuration.
 2. The medical device ofclaim 1, wherein the constraining portion comprises a gathered sectionof the graft member.
 3. The medical device of claim 2, furthercomprising an attachment element joining first and second non-contiguousregions of the graft member to form the gathered section.
 4. The medicaldevice of claim 2, wherein the gathered section defines a passagewayadapted to permit a controlled amount of fluid flow through said bodyvessel in the second, opposite direction.
 5. The medical device of claim4, further comprising a cannula disposed in the passageway.
 6. Themedical device of claim 5, wherein the cannula comprises a distal enddisposed near the valve portion of the graft member and a proximal enddisposed near the constraining portion of the graft member, and whereinthe proximal end defines an opening angulated with respect to the graftmember.
 7. The medical device of claim 1, wherein the graft membercomprises an extracellular matrix material.
 8. The medical device ofclaim 1, wherein the graft member comprises small intestine submucosa.9. The medical device of claim 1, wherein the graft member defines anedge substantially free of the support structure, the edge cooperatingwith a portion of the support structure to define an opening adapted topermit a controlled amount of fluid flow through said body vessel in thesecond, opposite direction.
 10. The medical device of claim 9, whereinthe edge is defined by the constraining portion of the graft member. 11.A medical device for implantation in a body vessel, comprising: asupport structure; and first and second graft members connected to thesupport structure, each of the graft members comprising a valve portionand a constraining portion, the valve portions being disposedsubstantially opposite one another and adapted to cooperatively permitfluid flow through said vessel in a first direction and substantiallyprevent fluid flow through said vessel in a second, opposite direction;wherein the constraining portions cooperate to substantially prevent thesupport structure from achieving the second, expanded configuration. 12.The medical device according to claim 11, wherein one of theconstraining portions comprises a gathered section of the first graftmember.
 13. The medical device of claim 12, further comprising anattachment element joining first and second non-contiguous regions ofthe graft member to form the gathered section.
 14. The medical device ofclaim 12, wherein the gathered section defines a passageway adapted topermit a controlled amount of fluid flow through said body vessel in thesecond, opposite direction.
 15. The medical device of claim 14, furthercomprising a cannula disposed in the passageway.
 16. The medical deviceof claim 15, wherein the cannula comprises a distal end disposed nearthe valve portion of the graft member and a proximal end disposed nearthe constraining portion of the graft member, and wherein the proximalend defines an opening angulated with respect to the graft member. 17.The medical device of claim 11, wherein the graft member comprises anextracellular matrix material.
 18. The medical device of claim 11,wherein the graft member comprises small intestine submucosa.
 19. Amedical device for implantation in a body vessel, comprising: a supportstructure having a first, unexpanded configuration and a second,expanded configuration; means for preventing the support structure fromachieving the second, expanded configuration; and means for regulatingfluid flow through said body vessel.
 20. The medical device of claim 19,further comprising a graft member attached to the support structure;wherein the graft member defines the means for regulating fluid flowthrough said body vessel.
 21. The medical device of claim 20, whereinthe graft member further defines the means for preventing the supportstructure from achieving the second, expanded configuration.
 22. Themedical device of claim 19, further comprising a graft member attachedto the support structure; wherein the graft member defines the means forpreventing the support structure from achieving the second, expandedconfiguration.
 23. The medical device of claim 22, wherein the graftmember further defines the means for regulating fluid through said bodyvessel.
 24. A prosthetic valve for implantation in a body vessel,comprising: a support structure having a first, unexpanded configurationand a second, expanded configuration; a first valve leaflet connected tothe support structure and comprising a first valve portion and a firstconstraining portion; and a second valve leaflet connected to thesupport structure and comprising a second valve portion and a secondconstraining portion; wherein the first and second valve portionscooperatively regulate fluid flow through said body vessel; and whereinthe first and second constraining portions cooperatively prevent thesupport structure from achieving the second, expanded configuration.